Centerless grinding machine



June 5, 1963 J. s. BARTHOLOMEW 3, 3

CENTERLESS GRINDING MACHINE Filed Oct. 2, 1961 I INVENTOR. JERRY 6. BARTHOLOMEW g 9 VIA/40w.

fii 'ORNEYs Umkd tes Patent 3,094,817 CENTERLESS GRINDING MACHINE Jerry S. Bartholomew, Milford, Ohio, assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed Oct. 2, 1961, Ser. No. 142,118 4 Claims. (Cl. 51-103) The present invention relates to a workrest for a centerless grinding machine and is particularly adapted for supporting small diameter workpieces during a grinding operation.

A demand has been created in recent years for accurate production of parts of very small dimensions, for example, microliter syringe plungers. These parts are ground in the form of short lengths of Wire of small diameter and the completed parts must be extremely round in the diametral section and very straight end to end. In addition the surface finish must be smooth and uniform. Precision centerless grinding is an accepted operation to produce straight cylindrical work with a good surface finish but the support of small diameter workpieces presents many problems for which solutions have been difficult to find. Development of a relatively rigid workrest which will extend through the grinding area in the small space available between the grinding wheel and the regulating wheel of a centerless grinding machine has been a major problem in small diameter grinding operations where finished workpiece diameters are in the neighborhood of .020 inch or less.

7 It is therefore an object of this invention to pnovide a workrest blade and a blade support which is adapted for use in the centerless grinding of extremely small diameter workpieces.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

A centerless grinder workrest blade constructed in accordance with the preferred form of this invention utilizes a thin strip blade held under tension through the grinding area between the grinding wheel and the regulating wheel. That portion of the blade which is in the grinding area is supported from its ends and it not backed up by other structure in the grinding area. The rigidity of the blade is provided by the tensile stress therein which opposes deflection and tends to reduce the magnitude of the vibrations of the blade.

A clear understanding of the operation and construction of the workrest blade and support of this invention may be obtained from the following detailed description and the attached drawings wherein:

FIG. 1 is a perspective view of a centerless grinder workrest blade and support.

FIG. 2 is a section through the blade and support of FIG. 1.

FIG. 3 is a partial plan View of the workrest blade.

As shown in FIG. 1, the grinding wheel 10 is rotatably supported in a wheelhead 12 on the machine base 14. The regulating wheel 16 (shown retracted away from the grinding wheel 10 to expose the workrest blade 18) is supported on a slide 15 which is movably received on the base 14. The regulating wheel 16 is supported in the housing '17 fixed on the slide 15 and is adapted to be rotated at a rate slower than the grinding wheel 10 to control the rate of rotation of a workpiece lying on the blade 18 and held thereon by the action of the grinding and regulating wheels 10, 16. In the grinding opera- Patented June 25, 1963 tion the regulating wheel 16 is operative to hold the workpiece in contact with the grinding wheel 10 which is abrasive and rotated at a high rate of speed to remove metal from the workpiece. The surface of the regulating wheel 16 drives the workpiece and prevents it from picking up the speed of the grinding wheel 10 but does not remove metal from the workpiece.

The workrest blade 18 is a thin strip of hard metal which extends through the grinding area between the wheels 10, 16. The blade 18 is supported at each end between pairs of guide plates 20, 22 and 24, 26 which are rigidly held in the upright portions 28, 30, respec tively, of the frame 32 which is received on the machine slide 15 and fixed thereto during grinding operations. One of the upright portions 28, 30 is located at 'each end of the grinding area defined between the wheels 10, 16. A pin 34 extends through the guide plates 20, 22 and an end of the blade 18 to secure that end of the blade between the plates 20, 22. A pin 36 extends through a slotted stud 38 which embraces the other end of the blade 18 in the notch 40 in the guide plates 24, 26 and secures this other end to the stud 38. The stud 38 extends loosely through a space between the plates 24, 26 in a direction axially away from the blade 18. A wing nut 42 is threadedly engaged with a portion of the stud 38 which extends from between the plates 24, 26. The wing nut 42 is advanced on the stud 38 to engage the plates 24, 26. The combination of the pin 36, stud 38, and wing nut 42 holds the end of the blade 18'between the plates 24, 26 and provides a mechanism by which a tensile stress may be created in the blade 18. The tensile stress holds the blade 18 rigid between the pairs of plates 20, 22 and 24, 26.

In FIG. 2, the guide plates 20, 22 and blade 18 are shown in section. Each of the plates 20, 22 has a blade aligning surface 44 and a work aligning surface 46 in stepped relationship. The plates 20, 22 are held in the upright portion 28 so that a blade slot is formed between the surfaces 44 in which the blade 18 is received. A work guide way is also formed between the surfaces 46 and guides a workpiece 49 as it passes between the plates 20, 22 in a grinding operation. The plates 24, 26 have similar stepped surfaces which perform the same functions at the other end of the blade 18. Thus, the plates 20, 22, 24, 26 not only align the blade 18, but also provide convenient entry and exit guide surfaces for a workpiece as it passes through the grinding area during a throughfeed grinding operation.

It will be appreciated that a thin strip of materia may be used for the blade 18. In one application of the invention, a blade of the dimensions .5 x .010 x 12 inches and supported in the described manner was found to be eifective for grinding a workpiece of 5 inches in length and .018 inch in diameter. The blade used was a strip of hardened and ground steel of the type commercially available for use as shim stock and feeler gauges and found as a stock item in most machine shops. Prior to use an angle of 30 degrees was ground on the upper surface 48 (FIG. 2) of the blade 18 on which a workpiece is supported. When supported and constructed in the described manner, such a blade 18 and supporting structure 32 do not interfere with the wheels 10, 16 when they are closed together to the proper spacing for producing the required small diameter. The blades of this type workrest are relatively inexpensive and are easily replaced in the event of an accident which might destroy or damage a blade and tooling costs are appreciably reduced.

What is claimed is:

1. In a centerless grinding machine having a base, a grinding wheel rotatably supported on the base, and a regulating wheel rotatably supported adjacent the grinding wheel, the space between the grinding and regulating wheels defining a grinding area, a device for supporting workpieces in the grinding area comprising a thin strip workrest blade non-rigid when tensilely unstressed, and means at each end of the grinding area to hold an end of said blade for support thereof through the grinding area, said means operable to apply a longitudinal tensile stress to said blade whereby said blade is maintained rigid through the grinding area.

2. In a centerless grinding machine having a base, a grinding wheel rotatably supported on the base, and a regulating wheel rotatably supported adjacent the grinding Wheel on the base, the space between the grinding and regulating wheels defining a grinding area, a device for supporting workpieces in the grinding area comprising, a support frame received on the base between the grinding and regulating wheels and having an upright portion at each end of the grinding area, a thin strip workrest blade non-rigid when tensilely unstressed, means to secure one end of said blade to one of said upright portions, and means in the other upright portion to hold the other end of said blade and to apply longitudinal tension thereto, said means to secure and means to hold maintaining said blade taut through the grinding area to provide rigidity of said blade.

3. In a centerless grinding machine having a base, a grinding wheel rotatably supported on the base, and a regulating wheel rotatably supported adjacent the grinding wheel on the base, the space between the grinding and regulating wheels defining a grinding area, a device for supporting workpieces in the grinding area cornprising, a support frame received on the base between the grinding and regulating wheels and having an upright portion at each end of the grinding area, a thin strip workrest blade non-rigid when tensilely unstressed, and a pair of guide plates in each of said upright portions, the

guide plates in one upright portion having means to secure one end of said blade therebetween, the guide plates in the other of said upright portions having a mechanism operable to hold the other end of said blade and to apply a tensile stress thereto whereby said blade is maintained taut through the grinding area to provide rigidity of said blade.

4. In a centerless grinding machine having a base, a grinding wheel rotatably supported on the base, and a regulating wheel rotatably supported adjacent the grinding Wheel on the base, the space between the grinding and regulating wheels defining a grinding area, a device for supporting workpieces in the grinding area comprising, a support frame received on the base between the grinding and regulating wheels and having an upright portion at each end of the grinding area, a thin strip workrest blade non-rigid when tensilely unstressed, and a pair of guide plates in each of said upright portions, each plate of said pairs having a blade aligning surface and a work aligning surface on one side thereof in stepped relationship, the plates of each pair held together in each of said upright portions to form a blade slot and a guide way respectively between said blade and work aligning surfaces adapted to receive said blade and to guide a workpiece thereon, one of said pairs having means to secure one end of said blade in said slot thereof and the other of said pair having means to hold the other end of said blade in said slot thereof and to apply a tensile stress thereto whereby said blade is maintained taut through the grinding area to provide rigidity in said blade.

,Sanford Feb. 12, 1924 Horton May 14, 1957 

1. IN A CENTERLESS GRINDING MACHINE HAVING A BASE, A GRINDING WHEEL ROTATABLY SUPPORTED ON THE BASE, AND A REGULATING WHEEL ROTATABLY SUPPORTED ADJACENT THE GRINDING WHEEL, THE SPACE BETWEEN THE GRINDING AND REGULATING WHEELS DEFINING A GRINDING AREA, A DEVICE FOR SUPPORTING WORKPIECES IN THE GRINDING AREA COMPRISING A THIN STRIP WORKREST BLADE NON-RIGID WHEN TENSILEY UNSTRESSED, AND MEANS AT EACH END OF THE GRINDING AREA TO HOLD AN END OF SAID BLADE FOR SUPPORT THEREOF THROUGH THE GRINDING AREA, SAID MEANS OPERABLE TO APPLY A LONGITUDINAL TENSILE STRESS TO SAID BLADE WHEREBY SAID BLADE IS MAINTAINED RIGID THROUGH THE GRINDING AREA. 